Overview Information

Theanine is an amino acid found in tea. It is also found in some mushrooms. It is similar in structure to glutamic acid, another amino acid.

Some people take theanine by mouth for anxiety and stress, depression, schizophrenia, for preventing Alzheimer's disease, for treating attention deficit-hyperactivity disorder (ADHD), and improving mental performance and attention. Theanine is also taken by mouth for reducing blood pressure, preventing the flu, and improving how well cancer drugs work as well as decreasing the side effects of cancer drugs.

How does it work?

Theanine has a chemical structure very similar to glutamate, a naturally occurring amino acid in the body that helps transmit nerve impulses in the brain. Some of the effects of theanine appear to be similar to glutamate, and some effects seem to block glutamate.

Uses & Effectiveness?

Possibly Effective for

Mental performance. Taking theanine before a test seems to help reduce errors. Taking theanine with caffeine seems to improve a person's ability to switch attention between different tasks.

Insufficient Evidence for

Attention. Early research shows that taking 200 mg of theanine before a test improves attention. Taking theanine with caffeine seems to work better than taking theanine alone. Taking lower doses of theanine might not improve attention.

Mild mental impairment. Early research shows that taking a product containing theanine and green tea might improve memory or attention in people with mild mental impairment.

Colon cancer. Taking a product containing cysteine and theanine might reduce side effects such as diarrhea and loss of appetite cause by some cancer drugs. This might help people with colon cancer complete cancer drug therapy.

Depression. Early research shows that taking theanine by mouth at bedtime for 8 weeks decreases symptoms and improves sleep in people with depression.

Stomach cancer. Taking theanine plus cysteine doesn't seem to reduce side effects such as diarrhea and loss of appetite cause by some cancer drugs in people with stomach cancer. It also doesn't seem to help people with stomach cancer complete cancer drug therapy.

Influenza (flu). Early research shows that taking a combination of green tea extract plus theanine daily for 5 months may lower the risk of developing the flu.

Schizophrenia. Early research shows that taking theanine by mouth along with antipsychotic drugs reduces positive symptoms of schizophrenia. But it doesn't appear to reduce negative symptoms.

Stress. The effects of theanine on stress are conflicting. Some early research shows that taking 200 mg of theanine before an exam reduces anxiety and may prevent blood pressure from increasing due to stress. Other early research shows that taking 200 mg of theanine twice daily before and during pharmacy practice decreases stress levels. However, another early study shows that taking 200 mg of theanine helps promote tranquility in people who are already relaxed. But it doesn't work in people who are stressed. Reasons for the conflicting results are not clear.

Other conditions.

More evidence is needed to rate the effectiveness of theanine for these uses.

Side Effects & Safety

Theanine is POSSIBLY SAFE when taken by mouth, short-term. Doses of up to 400 mg of theanine daily have been safely used for 8 weeks. A specific product containing theanine and other green tea ingredients has also been used safely once daily for up to 5 months. It is not known if theanine is safe when used for longer periods of time. Theanine may cause mild adverse effects, such as headache or sleepiness.

Special Precautions & Warnings:

Pregnancy and breast-feeding:There is not enough reliable information about the safety of using theanine if you are pregnant or breast-feeding. Stay on the safe side and avoid use.

Children: Theanine is POSSIBLY SAFE for children when taken by mouth, short-term. Doses of 200 mg of theanine have been safely used twice daily for up to 6 weeks in boys aged 8-12 years.

Stimulant drugs speed up the nervous system. By speeding up the nervous system stimulant medications can make you feel jittery and speed up your heartbeat. Theanine might work to slow down the nervous system. Taking theanine along with stimulant medications might decrease the effectiveness of stimulant medications.<br/><br/>
Some stimulant drugs include diethylpropion (Tenuate), epinephrine, phentermine (Ionamin), pseudoephedrine (Sudafed), and many others.

Dosing

The following doses have been studied in scientific research:

ADULTS

BY MOUTH:

For mental performance: A single dose of 100 mg of theanine before a test has been used. Theanine has also been used in combination with caffeine. Combination doses have ranged from 30-100 mg of caffeine and 12-100 mg of theanine.

Find More Vitamins Used to Treat these Conditions

CONDITIONS OF USE AND IMPORTANT INFORMATION:
This information is meant to supplement, not replace advice from your doctor or healthcare provider and is not meant to cover all possible uses, precautions, interactions or adverse effects. This information may not fit your specific health circumstances. Never delay or disregard seeking professional medical advice from your doctor or other qualified health care provider because of something you have read on WebMD. You should always speak with your doctor or health care professional before you start, stop, or change any prescribed part of your health care plan or treatment and to determine what course of therapy is right for you.